1. Field of the Invention
This invention relates to the chemical arts. In particular, it relates to flavor systems containing encapsulated volatile flavoring materials.
2. Discussion of the Prior Art
Much work has been directed at developing flavor systems to create or to enhance flavors in a variety of foods, including foods that are consumed only after relatively long periods of storage, such as butter-flavored microwavable popcorn. Critical to the effectiveness of many of the flavoring materials used in the flavor systems is the materials' ability to stimulate the sense of smell, instead of or in addition to stimulating the sense of taste. Consequently, flavor systems often contain aromatic substances or other materials that are inherently volatile.
Because of their volatility, these materials can be lost from a flavor system or a food containing such a flavor system via evaporation during storage. The extent of loss of each aromatic substance or other volatile flavoring material depends upon, among other factors, the temperature the flavor system or food is stored, the time it is stored at this temperature, and the vapor pressure of the flavoring material. Thus, although a flavor system initially may be carefully formulated to impart the desired flavor or fragrance to the food, upon standing there can be a significant change in the overall flavor or fragrance as the volatile flavoring materials are lost. Thus, the appeal of a food containing such a flavor system may depend on when it is consumed.
Of course, the stability of a flavor system or of a food containing such a flavor system, over the time between initial formulation and consumption, is not the only significant criteria in developing the flavor system. It is also important that the flavor, once preserved, is released when the food is consumed.
Butter-flavored foods are highly desirable and widely consumed. For example, in recent years butter-flavored microwavable popcorn has become extremely popular. It is widely recognized within the art of producing and using butter flavors that diacetyl and butyric acid are key flavor components easily lost via evaporation (Merker, U.S. Pat. No. 2,773,772; Buhler, U.S. Pat. No. 3,653,921; Millisor, U.S. Pat. No. 4,384,008; Bakal, U.S. Pat. No. 4,414,229; and Darragh, U.S. Pat. No. 3,867,556). Buhler, U.S. Pat. No. 3,653,921, for example, notes the prior art has suggested the incorporation of selected lactones, diacetyl, constituents of cultured butter, short-chain fatty acids and alcohols and other chemical compounds into oleaginous foodstuffs to impart a butter flavor. Millisor, U.S. Pat. No. 4,384,008, discloses a specific formulation made from diacetyl, several short-chain fatty acids and lactones for preparing a butter flavored oil.
It would also be desirable to incorporate methyl sulfide into flavoring systems used for microwavable popcorn. If methyl sulfide, which is highly volatile, is stabilized, it can be used as a supplement to the valuable "corn" flavor of the popcorn itself.
It is known in the art to try to stabilize volatile flavoring materials by the process of encapsulation, whereby the volatile flavoring materials become enveloped or encased within a suitable coating. Materials and techniques for encapsulation or microencapsulation have been reviewed by Taylor [(A. H. Taylor, Food, 48-52 (1982)]and Dziezak [(J. D. Dziezak, Food Technology, 136-153 (1988)].
Currently, the most widely used technique is spray drying. With spray drying a volatile substance is first emulsified in an aqueous solution of a water-soluble protective colloid, such as a gelatin, gum arabic, starch or dextrin. The emulsion is then sprayed into a column of heated air or gases to evaporate the water. The resulting dry particles have a water-soluble shell or capsule of the water-soluble colloid in which the flavor is embedded or encapsulated in the form of minute droplets.
Several flavoring materials designed for specific butter flavor applications have been stabilized by spray drying with water-soluble colloids. Buhler, U.S. Pat. No. 3,653,921, for example, describes a butter flavored concentrate made into a dry free flowing form by spray drying. Millisor, U.S. Pat. No. 4,384,008, discloses a butter-flavored oil containing a spray dried component; two patents to Bakal, U.S. Pat. Nos. 4,414,229 and 4,844,921, disclose a natural butter flavor for margarine and butter flavored granules, respectively, containing spray dried flavoring components.
Such spray-dried materials protect the flavor components in the absence of water and release the material as soon as the flavor particle comes into contact with water. As pointed out in Smith, U.S. Pat. No. 3,819,838, this means spray dried particles are unsuitable for storage with water or moist ingredients. Consequently, spray dried particles are generally ill-suited for use in food products containing more than about 3% moisture. This includes popcorn, because the performance of popcorn kernels depends on, among other things, their having a significant moisture content. Popcorn kernels having at least 11.5% moisture are preferred, with moisture contents of from 13-14% most preferred. Because at least some of the moisture freely migrates through the popcorn kernel, water can migrate into sprayed dried flavoring materials, thus affecting the integrity of their coatings. Accordingly, spray drying has not proved a satisfactory answer to stabilizing the volatile materials used to flavor microwavable popcorn and other food products having significant moisture levels.
Darragh, U.S. Pat. No. 3,867,556 discloses the stabilization of a flavor active material by double encapsulating the material--first in a heat-release, water-insoluble shortening having a melting point of from about 120.degree. F.(49.degree. C.) or higher and then in an oil-insoluble, water-soluble material. The product is initially encapsulated by forcing a dispersion of flavoring material in melted shortening through a nozzle, thereby atomizing the material and forming it into microscopic drops, and allowing the dispersion to cool and solidify.
The product is then again encapsulated, this time by means of a fluidized bed. Air is forced upward through the bed, so the single encapsulated product undergo a continuous circular, tumbling action. The moving particles are sprayed with a solution of a water-soluble, oil-insoluble material to form the second layer of encapsulation. For the flavoring material to be released, not only must the outer layer come into contact with water, but the product must be subjected to a temperature greater than about 120.degree. F., for a time sufficient to melt the inner layer.
Consequently, there is a need for stabilized volatile flavoring materials, such as stabilized diacetyl, that are not lost during the storage of food products, such as microwavable popcorn. Further, there is a need for stabilizing volatile flavoring materials that can be used in microwavable foods, such as microwavable popcorn. Microwavable foods present problems not encountered if the food is not cooked prior to consumption or if the popcorn is prepared using other methods of cooking. One of the most important differences is that cooking times are generally much less with microwave cooking than with traditional methods. Consequently, for any stabilized flavor system to be useful with microwavable foods, such as microwavable popcorn, an effective amount of the flavor must be released under the microwave cooking conditions.
Therefore, there has existed a definite need for stabilizing volatile flavors, so that their aroma and taste does not change as a function of time. There has further existed a need for flavor systems that release an effective amount of flavor under microwave cooking conditions. The present invention satisfies these and other needs and provides further related advantages.